Field of the Invention
The invention relates to a radiation-emitting semiconductor chip having an active layer and a large number of side surfaces that bound the extent of the active layer at the sides.
The invention also relates to a method for producing a radiation-emitting semiconductor chip, in which an active layer is formed above one surface of a substrate, and in which the substrate is then separated together with the active layer in order to form semiconductor chips.
Published, Japanese Patent Application JP 10-32 69 10 A discloses a radiation-emitting semiconductor chip which is in the form of a truncated pyramid. The active layer of the known semiconductor chip is located in a central area of the semiconductor chip. Crystalline layers are located above the active layer. The base surface, which runs parallel to the active layer, is diamond-shaped. The particular configuration of the base surface makes it easier for light to emerge from the semiconductor chip. This is because the light beams strike an outer surface at an angle that is less than the critical angle, at the latest after a number of total reflections. The photon output efficiency is relatively high owing to the particular configuration of the semiconductor chip, which is in the form of a truncated pyramid.
One disadvantage of the known semiconductor chip is that the cross-sectional area between the base surface (which is used for an electrode to be applied to) and an opposite upper face, which is likewise provided with an electrode, varies. The fact that the cross section of the semiconductor chip decreases toward the base surfaces results in that it is harder for heat to be dissipated. Furthermore, the current flow is impeded by the reduced cross section, so that the resistance in the semiconductor chip is locally increased. These two factors together lead to a locally different increased thermal load on the semiconductor chip. The stresses that result from this in the semiconductor chip have an adverse effect, however, on the life of the semiconductor chip. Furthermore, the increased thermal load reduces the conversion efficiency of the active layer.